aboutsummaryrefslogtreecommitdiff
path: root/nbd/client-connection.c
blob: 3d14296c0424bf581c29dbdd4f4345314d317c9c (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
/*
 * QEMU Block driver for  NBD
 *
 * Copyright (c) 2021 Virtuozzo International GmbH.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "qemu/osdep.h"
#include "trace.h"

#include "block/nbd.h"

#include "qapi/qapi-visit-sockets.h"
#include "qapi/clone-visitor.h"
#include "qemu/coroutine.h"

struct NBDClientConnection {
    /* Initialization constants, never change */
    SocketAddress *saddr; /* address to connect to */
    QCryptoTLSCreds *tlscreds;
    char *tlshostname;
    NBDExportInfo initial_info;
    bool do_negotiation;
    bool do_retry;

    QemuMutex mutex;

    NBDExportInfo updated_info;
    /*
     * @sioc represents a successful result. While thread is running, @sioc is
     * used only by thread and not protected by mutex. When thread is not
     * running, @sioc is stolen by nbd_co_establish_connection() under mutex.
     */
    QIOChannelSocket *sioc;
    QIOChannel *ioc;
    /*
     * @err represents previous attempt. It may be copied by
     * nbd_co_establish_connection() when it reports failure.
     */
    Error *err;

    /* All further fields are accessed only under mutex */
    bool running; /* thread is running now */
    bool detached; /* thread is detached and should cleanup the state */

    /*
     * wait_co: if non-NULL, which coroutine to wake in
     * nbd_co_establish_connection() after yield()
     */
    Coroutine *wait_co;
};

/*
 * The function isn't protected by any mutex, only call it when the client
 * connection attempt has not yet started.
 */
void nbd_client_connection_enable_retry(NBDClientConnection *conn)
{
    conn->do_retry = true;
}

NBDClientConnection *nbd_client_connection_new(const SocketAddress *saddr,
                                               bool do_negotiation,
                                               const char *export_name,
                                               const char *x_dirty_bitmap,
                                               QCryptoTLSCreds *tlscreds,
                                               const char *tlshostname)
{
    NBDClientConnection *conn = g_new(NBDClientConnection, 1);

    object_ref(OBJECT(tlscreds));
    *conn = (NBDClientConnection) {
        .saddr = QAPI_CLONE(SocketAddress, saddr),
        .tlscreds = tlscreds,
        .tlshostname = g_strdup(tlshostname),
        .do_negotiation = do_negotiation,

        .initial_info.request_sizes = true,
        .initial_info.structured_reply = true,
        .initial_info.base_allocation = true,
        .initial_info.x_dirty_bitmap = g_strdup(x_dirty_bitmap),
        .initial_info.name = g_strdup(export_name ?: "")
    };

    qemu_mutex_init(&conn->mutex);

    return conn;
}

static void nbd_client_connection_do_free(NBDClientConnection *conn)
{
    if (conn->sioc) {
        qio_channel_close(QIO_CHANNEL(conn->sioc), NULL);
        object_unref(OBJECT(conn->sioc));
    }
    error_free(conn->err);
    qapi_free_SocketAddress(conn->saddr);
    g_free(conn->tlshostname);
    object_unref(OBJECT(conn->tlscreds));
    g_free(conn->initial_info.x_dirty_bitmap);
    g_free(conn->initial_info.name);
    g_free(conn);
}

/*
 * Connect to @addr and do NBD negotiation if @info is not null. If @tlscreds
 * are given @outioc is returned. @outioc is provided only on success.  The call
 * may be cancelled from other thread by simply qio_channel_shutdown(sioc).
 */
static int nbd_connect(QIOChannelSocket *sioc, SocketAddress *addr,
                       NBDExportInfo *info, QCryptoTLSCreds *tlscreds,
                       const char *tlshostname,
                       QIOChannel **outioc, Error **errp)
{
    int ret;

    if (outioc) {
        *outioc = NULL;
    }

    ret = qio_channel_socket_connect_sync(sioc, addr, errp);
    if (ret < 0) {
        return ret;
    }

    qio_channel_set_delay(QIO_CHANNEL(sioc), false);

    if (!info) {
        return 0;
    }

    ret = nbd_receive_negotiate(NULL, QIO_CHANNEL(sioc), tlscreds,
                                tlshostname,
                                outioc, info, errp);
    if (ret < 0) {
        /*
         * nbd_receive_negotiate() may setup tls ioc and return it even on
         * failure path. In this case we should use it instead of original
         * channel.
         */
        if (outioc && *outioc) {
            qio_channel_close(*outioc, NULL);
            object_unref(OBJECT(*outioc));
            *outioc = NULL;
        } else {
            qio_channel_close(QIO_CHANNEL(sioc), NULL);
        }

        return ret;
    }

    return 0;
}

static void *connect_thread_func(void *opaque)
{
    NBDClientConnection *conn = opaque;
    int ret;
    bool do_free;
    uint64_t timeout = 1;
    uint64_t max_timeout = 16;

    qemu_mutex_lock(&conn->mutex);
    while (!conn->detached) {
        Error *local_err = NULL;

        assert(!conn->sioc);
        conn->sioc = qio_channel_socket_new();

        qemu_mutex_unlock(&conn->mutex);

        conn->updated_info = conn->initial_info;

        ret = nbd_connect(conn->sioc, conn->saddr,
                          conn->do_negotiation ? &conn->updated_info : NULL,
                          conn->tlscreds, conn->tlshostname,
                          &conn->ioc, &local_err);

        /*
         * conn->updated_info will finally be returned to the user. Clear the
         * pointers to our internally allocated strings, which are IN parameters
         * of nbd_receive_negotiate() and therefore nbd_connect(). Caller
         * shoudn't be interested in these fields.
         */
        conn->updated_info.x_dirty_bitmap = NULL;
        conn->updated_info.name = NULL;

        qemu_mutex_lock(&conn->mutex);

        error_free(conn->err);
        conn->err = NULL;
        error_propagate(&conn->err, local_err);

        if (ret < 0) {
            object_unref(OBJECT(conn->sioc));
            conn->sioc = NULL;
            if (conn->do_retry && !conn->detached) {
                trace_nbd_connect_thread_sleep(timeout);
                qemu_mutex_unlock(&conn->mutex);

                sleep(timeout);
                if (timeout < max_timeout) {
                    timeout *= 2;
                }

                qemu_mutex_lock(&conn->mutex);
                continue;
            }
        }

        break;
    }

    /* mutex is locked */

    assert(conn->running);
    conn->running = false;
    if (conn->wait_co) {
        aio_co_wake(conn->wait_co);
        conn->wait_co = NULL;
    }
    do_free = conn->detached;

    qemu_mutex_unlock(&conn->mutex);

    if (do_free) {
        nbd_client_connection_do_free(conn);
    }

    return NULL;
}

void nbd_client_connection_release(NBDClientConnection *conn)
{
    bool do_free = false;

    if (!conn) {
        return;
    }

    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
        assert(!conn->detached);
        if (conn->running) {
            conn->detached = true;
        } else {
            do_free = true;
        }
        if (conn->sioc) {
            qio_channel_shutdown(QIO_CHANNEL(conn->sioc),
                                 QIO_CHANNEL_SHUTDOWN_BOTH, NULL);
        }
    }

    if (do_free) {
        nbd_client_connection_do_free(conn);
    }
}

/*
 * Get a new connection in context of @conn:
 *   if the thread is running, wait for completion
 *   if the thread already succeeded in the background, and user didn't get the
 *     result, just return it now
 *   otherwise the thread is not running, so start a thread and wait for
 *     completion
 *
 * If @blocking is false, don't wait for the thread, return immediately.
 *
 * If @info is not NULL, also do nbd-negotiation after successful connection.
 * In this case info is used only as out parameter, and is fully initialized by
 * nbd_co_establish_connection(). "IN" fields of info as well as related only to
 * nbd_receive_export_list() would be zero (see description of NBDExportInfo in
 * include/block/nbd.h).
 */
QIOChannel *coroutine_fn
nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
                            bool blocking, Error **errp)
{
    QemuThread thread;

    if (conn->do_negotiation) {
        assert(info);
    }

    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
        /*
         * Don't call nbd_co_establish_connection() in several coroutines in
         * parallel. Only one call at once is supported.
         */
        assert(!conn->wait_co);

        if (!conn->running) {
            if (conn->sioc) {
                /* Previous attempt finally succeeded in background */
                if (conn->do_negotiation) {
                    memcpy(info, &conn->updated_info, sizeof(*info));
                    if (conn->ioc) {
                        /* TLS channel now has own reference to parent */
                        object_unref(OBJECT(conn->sioc));
                        conn->sioc = NULL;

                        return g_steal_pointer(&conn->ioc);
                    }
                }

                assert(!conn->ioc);

                return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
            }

            conn->running = true;
            qemu_thread_create(&thread, "nbd-connect",
                               connect_thread_func, conn, QEMU_THREAD_DETACHED);
        }

        if (!blocking) {
            if (conn->err) {
                error_propagate(errp, error_copy(conn->err));
            } else {
                error_setg(errp, "No connection at the moment");
            }

            return NULL;
        }

        conn->wait_co = qemu_coroutine_self();
    }

    /*
     * We are going to wait for connect-thread finish, but
     * nbd_co_establish_connection_cancel() can interrupt.
     */
    qemu_coroutine_yield();

    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
        if (conn->running) {
            /*
             * The connection attempt was canceled and the coroutine resumed
             * before the connection thread finished its job.  Report the
             * attempt as failed, but leave the connection thread running,
             * to reuse it for the next connection attempt.
             */
            if (conn->err) {
                error_propagate(errp, error_copy(conn->err));
            } else {
                /*
                 * The only possible case here is cancelling by open_timer
                 * during nbd_open(). So, the error message is for that case.
                 * If we have more use cases, we can refactor
                 * nbd_co_establish_connection_cancel() to take an additional
                 * parameter cancel_reason, that would be passed than to the
                 * caller of cancelled nbd_co_establish_connection().
                 */
                error_setg(errp, "Connection attempt cancelled by timeout");
            }

            return NULL;
        } else {
            /* Thread finished. There must be either error or sioc */
            assert(!conn->err != !conn->sioc);

            if (conn->err) {
                error_propagate(errp, error_copy(conn->err));
                return NULL;
            }

            if (conn->do_negotiation) {
                memcpy(info, &conn->updated_info, sizeof(*info));
                if (conn->ioc) {
                    /* TLS channel now has own reference to parent */
                    object_unref(OBJECT(conn->sioc));
                    conn->sioc = NULL;

                    return g_steal_pointer(&conn->ioc);
                }
            }

            assert(!conn->ioc);

            return QIO_CHANNEL(g_steal_pointer(&conn->sioc));
        }
    }

    abort(); /* unreachable */
}

/*
 * nbd_co_establish_connection_cancel
 * Cancel nbd_co_establish_connection() asynchronously.
 *
 * Note that this function neither directly stops the thread nor closes the
 * socket, but rather safely wakes nbd_co_establish_connection() which is
 * sleeping in yield()
 */
void nbd_co_establish_connection_cancel(NBDClientConnection *conn)
{
    Coroutine *wait_co;

    WITH_QEMU_LOCK_GUARD(&conn->mutex) {
        wait_co = g_steal_pointer(&conn->wait_co);
    }

    if (wait_co) {
        aio_co_wake(wait_co);
    }
}